![]() A capacitor may be used to store the charge to lengthen the time constant of the gate circuit and therefore the width of the pulse. ![]() This pulse can vary with the amount of pressure which is applied, since higher pressures generate higher voltages which take longer to dissipate. Thus piezo switches produce a single, brief "on" pulse. In the case of piezo switches, the force could be compressive pressure that causes the (typically disc-shaped) piezo element to bend very slightly like a drumhead. The piezoelectric effect is the generation of electric charge when certain materials are under stress. After the voltage pulse is dissipated in the gate resistor, the FET turns back "off", its normal high impedance state. When the FET is on, current can flow through it as with a conventional metal contact-based switch. The charge generated by the piezoelectric element in the switch is typically used to turn on an integrated semiconductor device such as a field effect transistor (FET), causing the switch assembly's output to be active, or "on". This is where the piezo switch truly comes into its own – these switches will function regardless of the type of glove the user is wearing as the switch depends on pressure to operate, not human touch.īulgin’s range of piezo switches are vandal-resistant, waterproof and dustproof with an ingress protection rating of IP68 and IP69K, and the company’s range of highly durable capacitive touch switches will also soon be released.A piezo switch is an electrical switch based on the piezoelectric effect. They do however work with thin surgical gloves or specially designed conductive fibre gloves that will allow a charge to be passed from the hand to the switch. ![]() Pricewise, capacitive switches are typically cheaper than piezo switches from a raw materials perspectiveĪ user wearing thick gloves cannot operate a capacitive switch. So for devices that are meant to react only to human touch, then the capacitive touch switch is ideal for this purpose.Ĭapacitive switches are used in a wide selection of applications, from medical and laboratory equipment and food processing machinery to consumer applications such as appliances, vending machines and lift controls. The difference between the device itself and the fingertip is sensed, thereby triggering the switch.Ī piezo switch senses touch force or relies on a small force, while capacitive switches require a charge or electrode, typically generated from human touch. The switch uses body capacitance, making use of the electrical charge naturally carried by the human body. On the other hand, a capacitive switch, also known as a capacitance switch, requires just one electrode, which can be placed behind a non-conductive panel. ![]() While there are no mechanical moving parts within the switch, it does require sufficient pressure to be applied in order to deflect the ceramic layer within. The word piezo is derived from the Greek piezein, which means to squeeze or press. It reacts to the force of being touched and generates an electric charge, which effectively sends a signal that the button has been pushed.Ī piezo switch relies on mechanical displacement or bending of piezo ceramic - also known as the piezoelectric effect. The durability of these switches means they can withstand millions of actuations and require little to no maintenance.Ī piezo is a small disc comprised of two layers an inner ceramic layer and an outer layer usually made from a metallic substance. Typically they are installed flush with the control panel, and with no moving parts they are often highly wear-resistant, dustproof, waterproof and suitable for repetitive operation. Both types of switches are usually comprised of flat, metallic discs, sometimes surrounded by an illuminated ring that lights up when the switch is activated.
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